Sunday, March 7, 2010

LM75A setup

I made serious mistake during design of pumping station thinking LM75A has non-volatile memory for configuration parameters. Actually this IC haven’t such ability as store configuration between power-ups.

Fortunately I have connection to TWI pins on both sensor board and wiring, so decided to create some “hardware config file” basing on ATTiny13. I have created Arduino sketch to test approach and it is working just fine, but tiny13 has no hardware TWI implementation comparing to ATMega168. After some research over the net I found nice implementation of AVR-300 (Software TWI) by Peter Fleury: http://homepage.hispeed.ch/peterfleury/avr-software.html#libs 

Here are 2 PCBs, one is test board for LM75 sensor, second is ATTiny13 for software implementation of TWI:

Homebrew PCBs for LM75A digital thermometer and ATTiny13 based board to configure sensor

My configuration board is still not working despite simplicity of the library. I haven’t found why, but my guess is that internal RC oscillator is not suitable for this. Will try to run with external crystal today.

Update: I had made it working!

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